SU974141A1 - Device for counting particles by sizes - Google Patents

Description

 The invention relates to analytical instrumentation and can be used for rapid automatic determination of the number and size of particles suspended in various dispersion media, including for analyzing the dispersed composition of impurity particles contaminating various oils and fuels / as well as for determining their purity class.

Photometric devices are known for counting the number of particles and determining their size from the intensity of scattering or attenuation of light, which contain a flow cell, an illuminator that forms an illuminated recording area in the cell, a photodetector that differentiates radiation when scattered through this area, driver of the reference light signals and an electronic unit connected to the output

photodetector.

The electronic unit in these devices is a single or multi-threshold amplitude analyzer, through which the drying is the counting of electrical pulses through independent channels in

depending on their amplitude. The amplitude of the electrical pulses is proportional to the size of the particles, so the results of counting the pulses can be transformed into a histogram of the particle size distribution.

Since the optical schemes of these devices are constructed using a single-beam scheme, their sensitivity to the detection of pulses of radiation scattered by particles can be affected by various destabilizing factors, therefore, periodically the actual sensitivity of the device is adjusted by the signals produced by the driver of the reference light pulses. This allows the sensitivity to be maintained at the original level, as established during calibration, which is produced on monodisperse media with a known particle size of 1.

However, such monodisperse particles can only be selected.

25 in a narrow size range for a limited class of dispersed systems. Calibration of thresholds for polydisperse media does not allow to achieve the required accuracy after 0. The ambiguity of identifying the sensitivity threshold of a device to a particle of a certain size in a given environment. The wider the particle size distribution curve, the greater the calibration error. . The closest in technical essence to the invention is a device for counting particles by size, containing a flow cell, a radiation source, a photodetector, a shaper of reference light signals, and an electronic unit connected to the output of the photodetector. When flowing through the illuminated zone, the particles of the dispersed system under investigation scatter the light flux in the form of short flashes of light, which are transformed into electrical pulses by means of a photodetector. The latter arrive at the input of the electronic unit where, depending on the amplitude, the counting takes place in the corresponding channels. The shaper of the reference signals is designed as a rotating disk with holes. The amplitude of the light pulses is proportional to the actual sensitivity of the device. The shaper is turned on intermittently by measurements. In this case, by adjusting the gain of the electric unit, a threshold sensitivity is obtained at which the registration of the reference light pulses occurs in a predetermined counting channel of the electronic unit. This ensures the constant sensitivity of the entire device. The correspondence of the threshold sensitivity of the counting channels of an electronic block to particles of a certain size is determined by preliminary calibration of the device on monodisperse calibration media, the optical properties of which are identical to the properties of the medium being measured. At the threshold thresholds, the number of pulses registered in each channel corresponds to the number of particles passing through the cue, the sizes of which are within the thresholds of adjacent signals. The set of counting results for all channels gives a histogram of the size distribution of particles of the medium being measured. is the inadequate accuracy of determining the size of the particles being poured due to the absence of a wide class of investigated dispersed systems of calibration media with strictly monodic dispersed particles. The purpose of the invention is to increase the particle size determination. This goal is achieved by the fact that in a device for counting a part of the dimensions, comprising a flow-through light, a radiation source, photo-light. the miniature, the driver of the reference light signals and the electronic unit connected to the photodetector output, a calibration oscillator, a reciprocating oscillator, a reference cuvette, with the internal channel of the cuvette filled with the irradiated medium and blocked by grids, symmetrically from them from the axis of the radiation source, when In this case, between the grids there is a particle sized with a known optical properties, and one end of the cuvette is covered with an elastic membrane that is in contact with a reciprocating stimulator. nk oscillations. FIG. 1 shows a block diagram of the device, (top view); FIG. 72 is a calibration oscillator; section A-A in FIG. 1. The device contains a flow cell 1, which represents a translucent tube, a square tube, a radiation source 2, which forms the generated light radiation 3, a photodetector 4 connected to the input of the electronic unit 5 and a calibration oscillator b. Flow cell 1 and qcv, cylinder b are located on the bed 7, which is equipped with a means of movement. At one extreme position of the bed 7, an oscillator b is inserted at the point of intersection of the axes of the illuminator 2 and the photodetector 4. In the other extreme iHeM position, the flow cell 1. The oscillator b contains a reference cell 9 filled with a dispersion medium 8, the internal channel of which is blocked by two nets 10 and 11 spaced apart from each other, between which is located a particle 12 sized by mesh. 11 must be smaller than the particle size 12. The transparent tube on one side of the end is closed and on the other its end is blocked by an elastic membrane 13 that is in contact with the striker 14 and has a reciprocating motion 15. In the Calibration mode b alibrovochny oscillator is set at a point of intersection of the axes 2 and illuminating the photodetector 4. Simultaneously incorporated booster 15 vozvratnopostupatelnyh oscillations which oscillate through the membrane 13 and the dispersion medium 8 transmitted certified particle size 12. In the initial time portion is at ca .setke. As a result of the impact of the striker 14, the membrane bends, displacing the dispersion medium upwards. In this case, the particle crosses the light flux and is delayed by the grid 10.. When-, the reverse course of the striker membrane, and in addition. With it, the dispersion medium with the particle returns to its original position. With multiple baths, a particle scatters light pulses that imitate signals based on the flow of strictly monodisperse particles through a cell. Light signals are sensed by the photodetector 4 and transformed into proportional-electric pulses. The latter in the electronic unit 5 are used as calibration pulses to automatically adjust the coefficient of force to the level at which these pulses begin to register in the calibrated counting channel of the electronic unit.

After calibration, the oscillator is replaced by a flow cell, the device is switched to the Measurement mode. When a measured medium flows through a flow cell, at the moments when particles intersect flow 3 (detection zones), light pulses are formed, each of which is proportional in size to the size of the corresponding particle. The light signals after conversion in the photodetector come to the electronic unit, in which they are registered. At the same time in calibrated. Only those particles of the measured medium, which are identical in size and optical properties to the certified oscillator particle, are recorded in the counting channel of the electronic unit.

This device can significantly improve the accuracy of determination / size of the counted particles of a wide class of disperse systems of DPN, and simplify the calibration process.

Claims (2)

1. US Patent 953715, class 356-102, published. 1961. 2.Alexander E. Martens ,. Errors Counting of Particles Using Light Scattering, Journal of the Air Pollution Control Association, Oct. 1968, 10.10, 661 (prototype). jL -L